Automatic chalkboard erasing apparatus

ABSTRACT

An automatic chalkboard eraser consists of a body which spans the board and has bearings running along the top and bottom thereof, a plurality of erasers rotatably mounted in the body and bearing against the board, an electric motor carried by the body, and drive means connecting the motor, the erasers, and traverse means. Manual and automatic switches provide for operation of the device in either direction within limits.

May 8, 1973 States Patent 1 ilnite Chrisp 3,l63,943 1/1965 3,2l8,663ll/l965 Battista..............

[54] AUTOMATIC CHALKBOARD ERASING APPARATUS Primary Examiner-Leon G.Machlin Attorney-Bertram H. Mann et al.

[76 Inventor:

[22] Filed:

[57] ABSTRACT An automatic chalkboard eraser consists of a body whichspans the board and has bearings running along the top and bottomthereof, a plurality of erasers rotatably mounted in the body andbearing against the board, an electric motor carried by the body, anddrive means connecting the motor, the erasers, and

@MM 7 51 32 1 sl.. 3 n w ms 5 m i l 2 MUS mh c "NM We 8 l C e I ll UmF1]] 2 00 555 [ll traverse means. Manual and automatic switches providefor operation of the device in either direction within limits.

[56] References Cited UNITED STATES PATENTS 2,167,296 7/!939Farmer................................ ....l5/98 2 Claims, 8 DrawingFigures PATENTEDHAY' 8191s SHEET 2 BF 3 IN VE N TOR Billie R. ChrispATTORNEY PAIENI MAY' 8 191a SHEET 3 BF 3 mw m l I I l Billie R; ChrispIN VE N TOR A TTORNE Y AUTOMATIC CHALKBOARD ERASING APPARATUS BACKGROUNDOF THE INVENTION This invention relates to automatic chalkboard erasersand comprises a plurality of erasers rotatably mounted on aboard-spanning body with powering and control means therefore.

The effectiveness of a teacher or lecturer using a blackboard in hispresentation to a class or audience is materially affected to hisdisadvantage by the necessity of stopping blackboard work from time totime to erase and this stoppage becomes a progressively greaterdisadvantage as the size of the board and the expanse of coveragethereof increases. While some attempts have been made to provideautomatic chalkboard erasers, still such devices have notprovenparticularly successful and therefore are not generally used oravailable.

Consequently, an object of the present invention is to provide a novelchalkboard eraser with powering means and controls whereby the user mayat will drive the eraser in either direction and at a desired distanceacross a board which it is desired to clear.

Another object is to provide an automatic chalkboard eraser withconvenient means for removing accumulated chalk dust.

DETAILED DESCRIPTION OF THE DRAWINGS In the accompanying drawings whichillustrate the invention,

FIG. 1 is a perspective view showing the novel apparatus mounted on achalkboard.

FIG. 2 is a front elevation of the device with the protective coverremoved.

FIG. 3 is an enlarged vertical transverse section through the upper partof the mechanism.

FIG. 4 is a front elevation of the structure in FIG. 3, with theprotective cover mostly broken away.

FIG. 5 is an enlarged side view of the lower part of the mechanism,parts being shown broken away and sectioned.

FIG. 6 is a front elevation of the structure in FIG. 5 with the covermostly broken away and sectioned.

FIG. 7 is an inside (rear) view of one of the erasers enlarged.

FIG. 8 is a wiring diagram.

FIG. 1 shows a more or less conventional chalkboard 10 with top, bottomand side framing ll, l2, l3 and 14. The automatic eraser apparatus,generally designated spans the board from top rail 16 to bottom rail 17.The portion of apparatus 15 which is actually seen in FIG. 1 is theprotective casing including front wall 18, left side wall 19, top wall21 and an enlarged box-like bottom part 22. Mounted conveniently onfront wall 18 is the stop-start switch button 23 and forward and reverse(right and left hand movement) control switch buttons 24 and 25.

FIG. 2 shows the apparatus with the protectivecover 18-22 removed toexpose the mechanism. The apparatus consists principally of a longnarrow lightweight body plate 29 in which are rotatably mounted theeraser units, generally designated 30-43, inclusive, all substantiallyidentical and better illustrated in FIGS. 3-7 inclusive. An extensionplate 44 is adjustably secured by bolts 45 to the lower edge of bodyplate 29 and has a bracket plate 46 projecting outwardly from the rightedge thereof. Secured to plate 46 by bolts 47 are clevice elements 48which pivotally mount a lug 49 projecting sidewardly from an electricmotor 50. Motor shaft 51 extends through a slot 52 in plate extension 44and at its inner end rigidly mounts a sheave wheel 53 which is connectedby a belt 54 to a substantially larger speed reduction pulley wheel 55(FIGS. 5 and 6). A coil tension spring 56 connects motor 50 to bracketplate 46 for maintaining tension on drive belt 54.

The eraser assemblies may be better understood by reference to FIG. 3showing an outer sheave wheel or pulley 58 rigid with a floating shaft59 which is journaled in a guide bushing 60 secured to and projectinginwardly from an adjusting plate 61 through main body plate 29. At theinner end of shaft 59 there is secured a circular eraser unit, includingthe plate 62 bolted at 63a to an insert 63, itself secured in the end ofshaft 59 by a set screw 63b, and four segmental erasing pads 64 of feltor other suitable chalk erasing material. Insert 63 has a flat (notshown) for cooperation with set screw 63b. Between the felt blocks 64are radial slots 65 for a purpose to be described. A coiled spring 66 iscompressed between guide bushing 60 and plate 62 and causes the eraserblocks 64 to bear against the chalkboard with sufi'icient force toachieve their purpose and to float in order to move in and out in caseof a warped chalkboard or misaligned joints therein.

At the bottom of the body plate 29, previously mentioned sheave wheel 55has a shaft 70 journaled in a bearing bushing 71 secured in an adjustingplate 72 bolted to body plate extension 44. At the outer end of shaft 70there is provided a small sheave wheel 73. An idler sheave 74 on shaft75 is suitably journaled in body plate extension 44.

At the upper end of body plate 29 (FIGS. 3 and 4) a sheave wheel 76 on ashaft 77 is journaled in a bushing 78 secured in the body plate andcarrying at its inner end a drive pinion 79. Pinion 79 meshes with arack 80 secured to the undersurface of top rail 16, previouslymentioned, for driving the apparatus across the board. Sheave wheel 76as well as all of the driving sheaves on the eraser units, as 58 inFIGS. 3. and 4, are driven by a belt 82 which winds back and forth aboutthe pulleys, as best shown in FIG. 2, to rotate the erasers in oppositedirections, thence about top drive pulley 76 and bottom drive pulley 73.Additional belt adjustment or guide pulleys are shown at 83, 83a, 84 and85 along the straight run of belt 82. Drive pulley 73, of course, isdriven from the motor by means of pulleys 55 and 53 and belt 54. Thearrangement and relative sizes of the pulley wheels provide a properspeed reduction action.

In order to guide the apparatus along the board and maintain the properassembly therewith, there are provided guide rollers 86 and 87 forrunning in and along slots 88 and 89, respectively, in top and bottomrails 16 and 17. Upper guide rollers 86 are mounted on shafts 90received in bearings 91a in a bearing block 91 which is adjustablybolted, as at 91b in FIG. 4, to the upper extremity of body plate 29.Shims 91c provide for adjusting the spacing of plate 29 and the eraserunits rela- -tive to the chalkboard. Lower guide rollers 87 are mountedon shafts 92 extending through body plate extension 44 and securedthereto by means of spaced collars 93.

FIG. 8 shows a wiring schematic, including the electric motor 50 havingforward and reverse terminals 95 and 96, a common: return terminal 97,manual forward and reverse switches 24 and 25 and normally closed limitswitches 101 and 102. One side 98a of 1 10 volt or other power circuit98 breaks through manual on-off switch 23, thence divides in lines 99and 100, respectively, breaking in series through one manual directionalswitch 24 and one limit switch 101 and the other manual directionalswitch and and limit switch 102. Limit switches 101 and 102, shown inFIG. 6, respectively engage abutments on opposite board side framing l4and 13 to stop motor 50 at the edge of the board. Thus, if the apparatusarrives at the left edge of the board, the corresponding limit switch102 will be opened, but the opposite limit switch 101 will be closed.Then if the rightward, directional switch 24 is closed, the apparatuswill move oppositely until either the rightward directional switch 24 orthe corresponding limit switch is opened and vice versa.

OPERATION In order to operate the apparatus assembled as shown in FIG. 1and 2, manual switch 23 is first moved to the on position and then oneof the reversing switches 24 or 25 is actuated in accordance with thedesired direction of movement of the erasing apparatus. Motor 50 is thenenergized so as to cause rotation of pinion 79, to drive the apparatusacross the board and, at the same time, rotate the eraser units forobliterating chalk markings on the board. The erasers will followslightly overlapping paths so the entire board will be affected.Rotation of the eraser pads 64 will cause the collected chalk to bethrown out centrifugally through slots 65 and this will be caught withinthe protective casing and dropped to the bottom frame 12 which isgrooved to retain the collected dust. Preferably, sealing strips will beprovided along the side walls 19 of the casing, as at 104 in FIG. 1. Thecasing may be secured in position, as by readily removable bolts 106extending into the edges of the body plate and these may be readilyremoved in order to'remove the protective casing for access to themechanism.

In case it is desired to clean the bottom framing 12 and/or the eraserpads 64, loosening of bolts 45, which secure extension plate 44 to mainbody plate 29, will permit guide rollers 87 to be dropped out of theirslots in bottom rail 17 so that the entire mechanism can be removed.Thereupon, the erasers may be cleaned in position or may be removed fromtheir mounting and guiding shafts 59 for better cleaning or replacement.The procedure for removing the erasers for cleaning, without disengagingrollers 86 and 87 from their tracks, is as follows:

1. Remove cover and drive belt 82.

2. Remove set screw 63b in floating shaft 59 which 4, being sure toalign the flat or insert 63 with set screw 63b. Plate 29 and the carriederaser units may be adjusted to fit the chalkboard.

Thus, it is possible for an instructor or other person using achalkboard to easily and quickly obliterate all or any portion of themarkings thereon simply by pushing the on-off button and one of theforward or reverse buttons, which will cause the device to move acrossthe board obliterating chalk markings as it goes. Upon reaching one ofthe side frames, the corresponding limit switch will be opened and theapparatus automatically stopped in condition ready for its next traversein the opposite direction.

Various features may be modified as will occur to those skilled in theart and the exclusive use of all modifications as come within the scopeof the appended claims is contemplated.

lclaim: 1. Apparatus for erasing a chalkboard comprising railways formounting adjacent the board, a body member for spanning the board,cooperating bearings on spaced portions of said member and said railwaysmounting said member for traverse across the board and determination ofthe positioning of said member transversely of the board, a plurality oferaser units rotatably mounted on and projecting laterally of said bodymember, cooperating drive elements on said body member and at least oneof said rails, each of said eraser units incorporating other driveelements and segmentally separated erasing pads, a motor carried by saidbody member, power transmission means interconnecting said motor andsaid drive elements, controls for said motor for causing said bodymember and erasers to move at the will of the operator in eitherdirection along the board and to stop automatically upon reaching apredetermined position relative to the board, and housing means normallyencasing said body member and eraser units for collecting chalk dustdischarged centrifugally between said pads.

2. Apparatus for erasing a chalkboard comprising railways for mountingadjacent the board, a body member for spanning the board, cooperatingbearings on spaced portions of said member and said railways mountingsaid member for traverse across the board and determination of thepositioning of said member transversely of the board, a plurality oferaser units rotatably mounted on and projecting laterally of said bodymember, cooperating drive elements on said body member and at least oneof said rails, each of said eraser units incorporating a shaft mountedon said body member for rotary and axial movements relative thereto, adrive element and eraser pad means on said shaft, andspring means urgingsaid pad means away from said body member, a motor carried by said bodymember, power transmission means interconnecting said motor and saiddrive elements, and controls for said motor for causing said body memberand erasers to move at the will of the operator in either directionalong the board and to stop automatically upon reaching a predeterminedposition relative to the board.

1. Apparatus for erasing a chalkboard comprising railways for mountingadjacent the board, a body member for spanning the board, cooperatingbearings on spaced portions of said member and said railways mountingsaid member for traverse across the board and determination of thepositioning of said member transversely of the board, a plurality oferaser units rotatably mounted on and projecting laterally of said bodymember, cooperating drive elements on said body member and at least oneof said rails, each of said eraser units incorporating other driveelements and segmentally separated erasing pads, a motor carried by saidbody member, power transmission means interconnecting said motor andsaid drive elements, controls for said motor for causing said bodymember and erasers to move at the will of the operator in eitherdirection along the board and to stop automatically upon reaching apredetermined position relative to the board, and housing means normallyencasing said body member and eraser units for collecting chalk dustdischarged centrifugally between said pads.
 2. Apparatus for erasing achalkboard comprising railways for mounting adjacent the board, a bodymember for spanning the board, cooperating bearings on spaced portionsof said member and said railways mounting said member for traverseacross the board and determination of the positioning of said membertransversely of the board, a plurality of eraser units rotatably mountedon and projecting laterally of said body member, cooperating driveelements on said body member and at least one of said rails, each ofsaid eraser units incorporating a shaft mounted on said body member forrotary and axial movements relative thereto, a drive element and eraserpad means on said shaft, and spring means urging said pad means awayfrom said body member, a motor carried by said body member, powertransmission means interconnecting said motor and said drive elements,and controls for said motor for causing said body member and erasers tomove at the will of the operator in either direction along the board andto stop automatically upon reaching a predetermined position relative tothe board.